This local change was lost during the fixing of issue17192 to update

gpshead · gpshead · commit 910bfb7bebac · 2013-04-30T00:05:25.000-07:00
libffi to 3.0.13.  (i'm not sure if it is needed anymore but see
issue 10309 for details which makes no mention of upstream; this
change is already in 3.3 and 3.4 but may need reapplying to 2.7
as done here)
diff --git a/Modules/_ctypes/libffi/src/dlmalloc.c b/Modules/_ctypes/libffi/src/dlmalloc.c
@@ -457,6 +457,11 @@ DEFAULT_MMAP_THRESHOLD       default: 256K
 #define LACKS_ERRNO_H
 #define MALLOC_FAILURE_ACTION
 #define MMAP_CLEARS 0 /* WINCE and some others apparently don't clear */
+#elif !defined _GNU_SOURCE
+/* mremap() on Linux requires this via sys/mman.h
+ * See roundup issue 10309
+ */
+#define _GNU_SOURCE 1
 #endif  /* WIN32 */
 
 #ifdef __OS2__
